Conventionally, there has been proposed a technology of authenticating a person based on preliminarily stored feature information of a face image, from a face region of a person included in video data captured by a monitoring camera or the like. In this case, feature information is extracted from the face region included in the video data, and the extracted feature information is compared with the preliminarily stored feature information to perform the person authentication.
In general, when photographing is performed by a monitoring camera or the like, the accuracy of person identification or recognition improves as the resolution of a photographed face region increases.
Also, since the resolution of a face region varies according to the conditions of photographing by a monitoring camera or the like, there may be a case where the resolution of the face region decreases. Recently, there have been proposed technologies of improving recognition accuracy even in the case where the resolution of a face region is low.
However, frequently, the size of a face of a person viewed in captured video data varies depending on how the monitoring camera is used. When there are different sizes of face regions viewed in video data, there will obviously be a difference in the resolution of faces of the people, thus degrading authentication accuracy.
For example, when the resolution of a face region of a person is low, there is a problem in that proper recognition results may not be obtained by a high-resolution recognition technique that is generally considered to be high in recognition accuracy. Therefore, a recognition technique applicable also to low resolution may be used. However, in this case, there is a problem in that high recognition accuracy may not be obtained when the resolution of a face region is high.
A monitoring camera installed in a high place captures an image while looking down from the high place. Therefore, when a person is close to the monitoring camera, the size (resolution) of a captured face is large but it is difficult for a face direction to be a front direction. When a person is remote from the monitoring camera, the direction of a face is likely to be a front direction but the size of a face is apt to decrease. Therefore, even when a monitoring camera captures a face of a person over a plurality of frame images, all the captured frame images are not necessarily frame images that can be used to perform high-accuracy person authentication, and the captured frame images may also include frame images reducing authentication accuracy.